Hundreds of people in Peru have needed treatment after visiting the site of what they believe is a meteorite crash. BBC News looks at the health issues.

What are the complaints?

The symptoms are varied - ranging from eye irritation to headaches, dizziness and nausea. Several police officers who visited the site had to be taken to hospital afterwards, and even a scientist wearing a mask at the scene declared the fumes were so strong his throat and nose flared up.

What does a meteorite emit?

Meteorites do not in themselves let off any dangerous fumes. They can however expose rotting organic matter, and the air can be filled with methane, hydrogen sulphide and carbon dioxide.

But there is some debate as to whether this is a meteorite - or indeed an object from space - in the first place.

Some scientists are suggesting that people may have witnessed a fireball, set off to investigate, and found a lake of sedimentary deposit that was already there. The biological process here could mean that the kind of fumes listed above are also emitted.

Can these really make people feel so ill?

Intense smells, even those that are not particularly toxic, can make people feel poorly, while high levels of carbon dioxide mean people at the site may not be getting enough oxygen.

At a purely physiological level, walking some way with some trepidation as to what one might find could well have an impact on the body and produce feelings of nausea and dizziness, sensations which may be compounded by the fact that other people say they are suffering from the same complaint.

So could mass hysteria play a role?

Symptoms could well be caused in part by what is known as a Mass Sociogenic Illness (MSI).

There are countless examples of this through history and up to the present day.

Amid fears of a gas leak late last year for instance, dozens of British pupils were taken to hospital with nausea and other symptoms. However no gas or environmental cause was found, and doctors could establish nothing wrong with the children. It was ascribed to mass hysteria.

Meanwhile, the Belgian Coke scare of 1999 - when many said they fell sick after drinking contaminated cans - was also said to be an example of MSI when laboratory analysis showed levels of contamination were not high enough to cause any of the illnesses reported.